The present invention relates in general to vehicle safety or seat belts and in particular to a new and useful take-up mechanism for automatically and partially retracting a safety belt during a vehicle emergency.
Take-up mechanisms serve the purpose of taking up the slack in a seat or safety belt of a vehicle, upon the occurrence of an impact on the vehicle, by pulling up the belt and thus minimizing the amount by which a passenger will be hurled forward, until the belt becomes effective. To obtain a satisfactory take-up, the belt must be retracted by about 20 cm. This corresponds to an angle of rotation of the belt reel in an automatic belt winding unit of about 550.degree..
A take-up mechanism is known from German AS No. 25 10 514, wherein two axially juxtaposed rotary vanes are provided on a piston shaft of a rotary piston motor, with a wing fixed to a housing of the mechanism and being associated with the first vane which forms a first expansion chamber with the wing. The second rotary vane is associated in a second expansion chamber with a rotary wing which is secured to a rotary cylinder and a ring at the belt reel side of the mechanism. To couple the ring to the belt reel, a plurality of bores is provided at the periphery of the adjacent side disc of the reel, into which a bolt is engageable which is drivable by the expanding gases of a drive charge (ignited upon abnormal vehicle motion due to an impact) and is provided on the ring at the belt reel side which is firmly connected to the rotary wing of the second expansion chamber. A notched wheel for a vehicle-controlled blocking of the automatic belt winding unit (operating upon abrupt but normal motion of the vehicle) is formed by the side disc facing the piston motor of the belt reel. The engaging sensor element for the notched wheel is designed as a small pawl for lifting a large pawl to be engaged with the notched wheel. The gases penetrating into the two expansion chambers turn the vane of the rotary piston shaft cooperating with the wing fixed to the housing, and also the second vane cooperating with the wing fixed to the ring. At the same time, the expansion space between the second vane and the wing secured to the ring enlarges, so that this wing produces almost two revolutions of the belt reel.
Disadvantageous in the prior art design is the relatively complicated construction of a rotary piston motor comprising two adjacent expansion spaces, the absence of a belt-controlled blocking mechanism (for blocking the belt when it is pulled abruptly, and the fact that the locking members must be massive casings in order to exhibit a satisfactory rigidity.